1. Field of the Invention
The present invention relates to a display.
2. Description of the Related Art
A known type of display comprises a static base unit and a rotating unit driven by a motor The rotating unit carries a plurality of light emitting diodes (LED's) which are controlled during rotation so as to provide a display image.
EP 0 26 762 discloses a display of this type in which a rotating two dimensional array of LED's sweeps a cylindrical volume and the LED's are controlled so as to define a cylindrical three dimensional array of picture elements (pixels). Data for controlling illumination of the pixels is sent in serial form from fixed electronics in the base unit via an infrared link to rotating electronics in the rotating unit. The rotating electronics essentially comprise a decoder for illuminating each LED of the array in sequence, with no data storage being provided in the rotating unit. Thus, only one LED at a time can be illuminated.
GB 2 093 617 and EP 0 156 544 disclose displays of this type in which two diametrically opposite vertical columns of LED's sweep a common cylindrical display surface and the LED's are controlled so as to define a cylindrical two dimensional array of pixels. The rotating unit contains enough electronics and memory for all of the LED's to be controlled simultaneously and for data to be stored for all of the pixels to provide one complete image. In order to change the displayed image, a connection has to be established with the rotating unit so that new data can be written into the memory. During such reprogramming, the display ceases to function as a display until the old data have been replaced by the new data. Thus, display images cannot be changed during normal operation of the display. This makes image updating and animation difficult or impossible and requires expert or trained personnel to reprogrammed the display.
Another problem with known displays of this type is that the light output is relatively low. Thus, shaded locations are necessary for viewing such displays.